18 Answers
18

In older versions of Ubuntu Ctrl + Alt + Del will bring up options for shutdown, restart, suspend and hibernate. these can then be selected with the arrow keys and Enter.

For a single hit solution in later versions you can use this script to create a keyboard short cut. First you need to download the scrip and save it on your computer. Next you need to make it executable by right clicking on it going to properties -> Permissions -> Allow executing file as a program. Finally go to System Settings -> Keyboard -> Shortcuts -> Custom Shortcuts and click the small plus symbol. For the command type in

/home/toby/power.sh shutdown

or whatever path you saved the script to.

Suspend, hibernate and restart are also availiable by this method, just replace shutdown in the above command.

If using unity press window key/superkey and then type shor and select keyboard shortcuts. Here you can then create a new shortcut then assign a key combo to shut your pc down...without using your power button! ;)

11.10 and later

Pressing Ctrl+Alt+Del leads to the logout dialog. If you need the old functionality back you will have to define your own shortcut by opening Keyboard -> Shortcuts from System settings and add this command:

gnome-session-quit --power-off

Alternatively we can use a shoutdown only dialog as shown in this answer

/usr/lib/indicator-session/gtk-logout-helper --shutdown

Note

Before we can use Ctrl+Alt+Del we will have to assign another shortcut to logout.

11.04 and earlier

Using default keyboard settings pressing Ctrl+Alt+Del will open the following window:

The first entry is selected by default for an immediate shutdown by just pressing Return in addition.

There also is a countdown that shuts down your system after 60s without any further keyboard action.

That's what I tried, but when I try to assign shortcut Ctl + Alt + Del logout window pops up, that's why I try to remove it in the first place :) When I try some other shortcut, it does not work as well, it just stays disabled.
–
umpirskyDec 28 '11 at 11:05

There are some low level keyboard shortcuts available. They talk directly to the kernel and can break things. You probably shouldn't use these. But in the interest of counter-acting the atrocious answers recommending this method, here's how to use the SysReq button to shutdown or reboot your system. If your cpu bursts into flames because of these incantations, well, can't say I didn't warn you.

Graceful

Reboot

There is a mnemonic here: busier backwards. As in, you are too busy to shutdown properly, so you are doing it backwards.

unRaw (take control of keyboard back from X),
tErminate (send SIGTERM to all processes, allowing them to terminate gracefully),
kIll (send SIGKILL to all processes, forcing them to terminate immediately),
Sync (flush data to disk),
Unmount (remount all filesystems read-only),
reBoot (durr)

Shutdown

This is the same except at the end use o for Off instead of b for reBoot.

alt +
SysRq +
r ,
e ,
i ,
s ,
u ,
o

Destructive

This is like yanking the power cord out. You risk destroying recently saved data (files not quite actually written to disk) and you will definitely lose anything unsaved. On the upside, it is quick and to the point.

reBoot:
alt +
SysRq +
b

shut Off:
alt +
SysRq +
o

Under graphical environments (such as GNOME or KDE) Alt+PrintScrn/SysRq+key combination generally only leads to a screenshot being dumped. To avoid this Print Screen feature the magic SysRq combination should include the Ctrl, becoming Ctrl+Alt+PrintScrn/SysRq+key. 1 That means, under graphical environments, to reboot this way, you need press the keyboard as follows:

After install Gnomenu, I found out another simple way to shutdown the computer immediately without choosing any option. Just add this python -u /usr/lib/gnomenu/session-manager.py shutdown to keyboard shortcut with your favorite shortcut to shutdown computer. I myself use Super+F4.
Hope this help :D

If you are using an ubuntu version prior to 11.04, the easiest way I have found to shutdown the computer via keyboard is to type: Super + S, Up, Enter

You will be offered a prompt that asks for verification that you want to shutdown. But you can eliminate this prompt by making a configuration change in the gconf-editor. Then the shortcut I posted above will directly and quickly shutdown the computer without prompt.

If your GUI ubuntu desktop is not freezed, open a terminal by Ctrl+Alt+T shortcut and do the following:

To shutdown now :

sudo shutdown -P now

To restart now :

sudo shutdown -P -r now

To shutdown after (say) 20 minutes :

sudo shutdown -P 20

Similarly, for restart also replace now by 20.

(To stop timed execution: Say after 15 minutes you decide not needed to shutdown/restart then go to the terminal window in which you executed the command and press Ctrl+C.)

If your GUI ubuntu desktop is freezed, go to commandline ubuntu desktop by Ctrl+Alt+F1(Here in place of F1, the keys F1to F6 are applicable ; also Ctrl+Alt+F7 will give you the GUI desktop back). Now in commandline ubuntu enter your login username and password. After successful login execute the same commands described above for shutdown (or restart).

Best is Ctrl+Alt+Del as many have said. That's the best way (especially for non-advanced users). If you wanna do it more 'geekily',then try opening a terminal and typing in the command (halt I think it was).

[ If the system is not responding, you can do Ctrl+Alt+Backspace which will forcefully log out of the system. (It won't shut down, just log off). I believe it's a safer alternative to the 'SysResq' key combo. ]

C+A+Bksp will shut down the X server (not enabled by default in new Ubuntu installs, you need to enable this in Keyboard options), bringing you back to GDM (user login); if you have graphical login, this will indeed log you out - in a rather forceful way. You are correct that this is somewhat safer than messing with SysRq, but it's still an emergency option at best.
–
PiskvorJul 20 '11 at 11:28

1

To succeed, the halt command must be run as root (so run sudo halt instead of just halt). Also, by default, Ctrl+Alt+Backspace doesn't actually do anything on an Ubuntu system. You can use Alt+SysRq+K instead, or you can re-enabled it by editing a configuration files. Details here.
–
Eliah KaganAug 4 '12 at 19:10

I believe that there's some sysRequest short cut but I know of only two... They're useful to me so if you want to reboot hit sysRequest+alt then type REUSB if you want to shut down always sysRequest+alt and type RSEOUI
Hope that will help ;]

You seem to be offering a cargo-cult incantation ("this is magic - it works, but I have no idea how"): unRaw, tErminate, Unmount, Sync, reBoot? If you've umounted the disks for writing, what is the point of syncing? (Hint: none) Also, RSEOUI is unRaw,Sync,tErminate,shut Off,Unmount,kIll - wtf? You're sending the last two commands to a computer that's turned off; also, the sync is pointless as E will trigger a graceful exit - more disk writes. For more info, see this: en.wikipedia.org/wiki/Magic_SysRq_key#Magic_commands Please don't give advice without knowing what it does.
–
PiskvorJul 20 '11 at 11:19

2

(Yes, your SysRq incantation will work - but somewhat accidentally. Note also that this is not a very clean way of initiating a shutdown.)
–
PiskvorJul 20 '11 at 11:21

Congratulations, you have directly shut off your system without any sort of cleanup - anything that's still in write caches will be lost, and non-journalled filesystems may get corrupt; that's not to mention any network connections. Your answer is technically correct - this will indeed reliably shut down the computer, but you may want to disconnect the hardware electrical plug instead - that's even more reliable, and has the same effect.
–
PiskvorJul 20 '11 at 11:25

@Piskvor While you're right that this is not a good way to shut down your computer, it is a little better than pulling the plug. The computer shuts itself off with this method. In particular, hard drives' read/write heads are unlikely to crash down onto the platters and physically damage the drive. But if the computer is not responding at all and must be force shut down (rather than restarted with Alt+SysRq+REISUB), Alt + SysRq + REISUO should be used (see this article).
–
Eliah KaganAug 4 '12 at 19:14

1

@Eliah Kagan: Oh, anything more sophisticated than physically cutting the power is (even if negligibly) better - and the "raising elephants" sequence which you mention is the accepted way of doing this - but still, the SysRq commands are an emergency, last-resort measure, to be used when everything else fails. (As for physical damage, any hard drives recent enough to be still operational - i.e. approximately 15 years old or newer - will automatically park themselves on power loss, so the risk of physical damage is very theoretical.)
–
PiskvorAug 6 '12 at 9:16